DTC P2097

DTC P2097:  Post Catalyst Fuel Trim System Too Rich (Bank 1)

General Description 

Courtesy of HONDA, U.S.A., INC.

The powertrain control module (PCM) detects oxygen content in the exhaust gas by the air/fuel ratio (A/F) sensor (sensor 1), and it uses feedback control before the warm up three way catalytic converter (WU-TWC) to bring the air/fuel ratio close to the target air/fuel ratio. The target air/fuel ratio is adjusted by the secondary heated oxygen sensor (secondary HO2S (sensor 2)) output so that the air/fuel ratio in the WU-TWC is optimized. When the A/F sensor (sensor 1) cannot measure air/fuel ratio in the exhaust gas normally, a gap occurs to the actual air/fuel ratio. As a result, the gap causes a deviation in target air/fuel ratio control (after WU-TWC) which is determined by the secondary HO2S (sensor 2). If the deviation exceeds a limit, the PCM detects a malfunction and stores a DTC.

Monitor Execution, Sequence, Duration, DTC Type 

Execution	Once per driving cycle*
Sequence	None
Duration	Depending on the driving conditions
DTC Type	Two drive cycles, MIL on

*: The malfunction judgment is cleared when it is judged as normal under the same driving conditions in which the malfunction is detected.

Enable Conditions 

Condition	Minimum	Maximum
Engine coolant temperature [ECT SENSOR 1]	156 deg. F (69 deg. C)	-
Intake air temperature [IAT SENSOR (1)]	19 deg. F (-7 deg. C)	-
Engine speed [ENGINE SPEED]	550 rpm	4, 000 rpm
Intake air amount	0.21 oz/second (6.0 g/second)	-
Fuel feedback	Closed loop

[ ]: HDS Parameter

Malfunction Threshold 

Either of the conditions is met:

• Short term fuel trim is higher than -0.01.
• Long term fuel trim is higher than 0.042.

Possible Cause 

NOTE:  The causes shown may not be a complete list of all potential problems, and it is possible that there may be other causes.

• A/F sensor (sensor 1) malfunction/slow response
• A/F sensor (sensor 1) circuit range/performance
• Fuel system too lean
• Fuel system too rich
• Secondary HO2S (sensor 2) circuit signal stuck lean
• Secondary HO2S (sensor 2) circuit high voltage
• Secondary HO2S (sensor 2) slow response
• Misfire
• Exhaust system failure (exhaust gas leak)

Confirmation Procedure 

Operating Condition 

• Start the engine. Hold the engine speed [ENGINE SPEED] at 3, 000 rpm without load (CVT in P or N, M/T in neutral) until the radiator fan comes on.
• Drive at a steady speed between 15 - 75 mph (25 - 120 km/h) and engine speed [ENGINE SPEED] 4, 000 rpm or less for at least 59 seconds.

• When freeze data is stored, drive the vehicle under those conditions instead of Driving Pattern step 2.
• Drive the vehicle in this manner only if the traffic regulations and ambient conditions allow.

With the HDS 

None.

Diagnosis Details 

Conditions for setting the DTC 

When a malfunction is detected during the first drive cycle, a Pending DTC is stored in the PCM memory. If the malfunction returns in the next (second) drive cycle, the MIL comes on and a Confirmed DTC and the freeze data are stored.

Conditions for clearing the DTC 

The MIL is cleared if the malfunction does not return in three consecutive drive cycles in which the engine conditions are similar to the first time the malfunction was detected. The MIL, the Pending DTC, the Confirmed DTC, and the freeze data can be cleared with the scan tool Clear command or by disconnecting the 12 volt battery.